[zkdkeen]

Hello, everyone!
I am using OpenFOAM 2.3.0 interDyMFoam to simulate the planning process of a certain boat. I have copied the DTCHull from the interDyMFoam tutorial, then changed the grid to my model grid, and made some other modification. After that, the computation is running well.

However, when I see the output log file, I did not find any information of the trim angle of my boat.

The output of one time step from my log file is as follows:

Interface Courant Number mean: 1.02311e-05 max: 5.03824
Courant Number mean: 0.00387547 max: 9.9856
deltaT = 8.32898e-05
Time = 1.087646


Restraint translationDamper:  force (-0 -29.8886 -0)
Restraint rotationDamper:  moment (-0 -0 -40.6732)
Centre of mass: (1.999 0.135179 0)
Linear velocity: (0 0.00348609 0)
Angular velocity: (0 0 0.00349454)
Execution time for mesh.update() = 1.36 s
GAMG:  Solving for pcorr, Initial residual = 1, Final residual = 0.0878525, No Iterations 13
time step continuity errors : sum local = 6.88552e-13, global = -4.13486e-13, cumulative = 7.49271e-07
smoothSolver:  Solving for alpha.water, Initial residual = 7.31488e-07, Final residual = 4.15881e-12, No Iterations 2
Phase-1 volume fraction = 0.613521  Min(alpha1) = -2.88339e-17  Max(alpha1) = 1
Applying the previous iteration compression flux
MULES: Correcting alpha.water
MULES: Correcting alpha.water
MULES: Correcting alpha.water
MULES: Correcting alpha.water
Phase-1 volume fraction = 0.613521  Min(alpha1) = -5.01782e-09  Max(alpha1) = 1
GAMG:  Solving for p_rgh, Initial residual = 0.000485961, Final residual = 4.47356e-07, No Iterations 11
time step continuity errors : sum local = 6.06207e-12, global = 3.72063e-12, cumulative = 7.49274e-07
GAMG:  Solving for p_rgh, Initial residual = 6.56915e-05, Final residual = 5.96469e-08, No Iterations 24
time step continuity errors : sum local = 8.08326e-13, global = 4.84482e-13, cumulative = 7.49275e-07
GAMG:  Solving for p_rgh, Initial residual = 3.83081e-05, Final residual = 4.69749e-08, No Iterations 24
time step continuity errors : sum local = 6.36565e-13, global = 3.72979e-13, cumulative = 7.49275e-07
smoothSolver:  Solving for omega, Initial residual = 2.03442e-07, Final residual = 4.6581e-10, No Iterations 1
bounding omega, min: -724.397 max: 1.08996e+06 average: 454.004
smoothSolver:  Solving for k, Initial residual = 2.63561e-06, Final residual = 5.50966e-09, No Iterations 1
bounding k, min: -4.08257 max: 43.585 average: 0.0755764
ExecutionTime = 81314.7 s  ClockTime = 81351 s

forces forces output:
    sum of forces:
        pressure : (77.6269 419.922 -166.705)
        viscous  : (3.34985 -0.269405 1.06011)
        porous   : (0 0 0)
    sum of moments:
        pressure : (1.78104 -10.2919 -34.4436)
        viscous  : (-0.346968 0.814481 1.01335)
        porous   : (0 0 0)

And the dynamicMeshDict file is as follows:

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.3.0                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      dynamicMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dynamicFvMesh       dynamicMotionSolverFvMesh;

motionSolverLibs    ("libsixDoFRigidBodyMotion.so");

solver              sixDoFRigidBodyMotion;

sixDoFRigidBodyMotionCoeffs
{
    patches         (hull);
    innerDistance   0.3;
    outerDistance   1;

    centreOfMass    (1.999 0.135 0);
    mass            39.08;
    momentOfInertia (1 1 40);
    rhoInf          1;
    report          on;
    reportToFile    on;
    accelerationRelaxation 0.3;
    value           uniform (0 0 0);

    constraints
    {
        yAxis
        {
            sixDoFRigidBodyMotionConstraint line;
            direction     (0 1 0);
        }
        zPlane
        {
            sixDoFRigidBodyMotionConstraint axis;
            axis          (0 0 1);
        }
    }

    restraints
    {
        translationDamper
        {
            sixDoFRigidBodyMotionRestraint linearDamper;
            coeff         8596;
        }
        rotationDamper
        {
            sixDoFRigidBodyMotionRestraint sphericalAngularDamper;
            coeff         11586;
        }
    }
}


// ************************************************************************* //

From that I can tell the sinkage from the centre of mass of each time step, but I can't get the trim angle information.


So, how can I get the trim angle? Should I do some modification in any of the dictionary files?


Any suggestion will be appreciated.

[zkdkeen]

No one has this kind of experience?

[JNSN]

Easiest would be to switch to the latest dev-Version:

https://github.com/OpenFOAM/OpenFOAM...73d888c26dfbbd

Best regards,
Jan

[zkdkeen]

Thanks Jan, I will check the latest version. Maybe I will start from a interDyMFoam tutorial.

But if we concentrate on this 2.3.0 version, is it possible to modify the code a little bit so that the Euler Angle could be printed as well?

Best regards,
Antoni

[zkdkeen]

With the new version of OF, I got the orientation from the output.

Note that, in my case, the ship is fixed in z=0 plane, which is different from the tutorial of DTCHull, so I think the orientation should be (cosφ −sinφ 0 sinφ cosφ 0 0 0 1). If your ship is fixed in y=0 plane, which is the same as the DTCHull tutorial, the orientation will change to (cosθ 0 sinθ 0 1 0 −sinθ 0 cosθ). Based on these information, the trim angle φ orθ can be easily calculated.

By searching in this forum, I've found some useful scripts provided by foamers. After that I modified them and added some new functions. Use this script, the trim angle and CG rise of a ship can be plotted directly.

motion.sh

#!/bin/bash
#pick centre of mass
grep 'Centre of mass' $1 | cut -d '(' -f 2 | tr -d ")" > centreMass_Extract
grep -e "^Time = " $1 | cut -d " " -f 3 > times_Extract
 
awk 'NR == 1 || (NR-1) % 3 == 0' centreMass_Extract > centreMass_Extract1
 
paste times_Extract centreMass_Extract1 > cmMotion_parcial
sed -e 's/ [ ]*/\t/g' cmMotion_parcial > cmMotion
 
 
#pick euler angle and convert it to degree
grep 'Orientation' $1 | cut -d '(' -f 2 | tr -d ")" > ort
awk 'NR == 1 || (NR-1) % 3 == 0' ort > ort1
 
awk '{ print $2 }' ort1 > sin_theta
  
awk '
function acos(x){return atan2(sqrt(1-x*x),x);}
function asin(x){return atan2(x,sqrt(1-x*x));}
function pi(){return 2*asin(1);}
{
        trim_in_deg=asin($1)/pi()*180
        print trim_in_deg 
}' sin_theta > trim_extract
paste times_Extract trim_extract > trimMotion
 
rm cmMotion_parcial
rm times_Extract
rm centreMass_Extract
rm centreMass_Extract1
 
rm ort
rm ort1
rm sin_theta
rm trim_extract
 
#plot cm and trim angle
gnuplot -persist > /dev/null 2>&1 << EOF
        set title "Motion vs. Time"
        set xlabel "Time / Iteration"
        set ylabel "CG Rise (m) or Trim Angle (degree)"
        
#        set xrange [3.06:]      
        plot    "cmMotion" using 1:3 title 'CG Rise' with linespoints,\
                        "trimMotion" using 1:2 title 'Trim Angle' with linespoints
EOF

montion.sh log

log is your output file of interDyMFoam solver.

Best regards,
Antoni